The present invention is generally directed to processes, and more specifically, to aggregation and coalescence processes for the preparation of polymer carrier coatings, especially conductive polymeric coatings. Carriers coated with the polymers obtained can be selected for known electrophotographic imaging, printing processes, including color processes, and lithography. In embodiments, the present invention is directed to a process for the preparation of conductive carrier coatings by aggregating submicron, about 50 to 200 nanometers, polymeric latex particles with a conductive component like carbon black by the addition of a cationic flocculant to form aggregates of an effective size, for example about 5 to about 10 microns in average volume diameter, and wherein the aggregates are held together primarily by electrostatic forces, and thereafter adding a known base component and heating for the primary purpose of reducing the aggregates to a size of from about 0.5 to about 1 micron in average volume diameter, and subsequently, coalescing at a temperature of from about above or at the resin or polymer glass transition temperature, Tg; and optionally washing and drying the conductive polymer obtained. The polymers obtained can be selected as carrier coatings for use in xerographic imaging and printing methods, including digital processes. The carrier particles can be prepared by a number of methods, such as blending and heating the conductive polymer particles obtained with a carrier core like iron, iron powder, steel, ferrites, and the like. The processes of the present invention in embodiments can be considered emulsion/aggregation processes, semi-reverse aggregation by the addition of a basic component.
There is illustrated in U.S. Pat. No. 4,996,127 a toner of associated particles of secondary particles comprising primary particles of a polymer having acidic or basic polar groups and a coloring agent. The polymers selected for the toners of the '127 patent can be prepared by an emulsion polymerization method, see for example columns 4 and 5 of this patent. In column 7 of this '127 patent, it is indicated that the toner can be prepared by mixing the required amount of coloring agent and optional charge additive with an emulsion of the polymer having an acidic or basic polar group obtained by emulsion polymerization. In U.S. Pat. No. 4,983,488, there is disclosed a process for the preparation of toners by the polymerization of a polymerizable monomer dispersed by emulsification in the presence of a colorant and/or a magnetic powder to prepare a principal resin component, and then effecting coagulation of the resulting polymerization liquid in such a manner that the particles in the liquid after coagulation have diameters suitable for a toner. It is indicated in column 9 of this patent that coagulated particles of 1 to 100, and particularly 3 to 70, are obtained. This process is thus directed to the use of coagulants, such as inorganic magnesium sulfate, which results in the formation of particles with a wide GSD. In U.S. Pat. No. 4,797,339, there is disclosed a process for the preparation of toners by resin emulsion polymerization, wherein similar to the '127 patent certain polar resins are selected.
Emulsion/aggregation processes for the preparation of toners are illustrated in a number of Xerox patents, the disclosures of which are totally incorporated herein by reference, such as U.S. Pat. No. 5,290,654, U.S. Pat. No. 5,278,020, U.S. Pat. No. 5,308,734, U.S. Pat. No. 5,346,797, U.S. Pat. No. 5,370,963, U.S. Pat. No. 5,344,738, U.S. Pat. No. 5,403,693, U.S. Pat. No. 5,418,108, U.S. Pat. No. 5,364,729, and U.S. Pat. No. 5,346,797.